A PW91-like exchange with a simple analytical form

A pair of families of generalized gradient approximation (GGA) exchange functionals is presented. The aim is to simplify the PW91 enhancement factor considerably, yet retain its shape, not degrade its performance and, within those confines, improve on it. The functionals are constructed non-empirically by taking as kernels the PBE and RPBE analytic forms and adding a Gaussian tail to comply with the asymptotic reduced-gradient constraint from non-uniform scaling. Standard heats of formation are considerably improved by the functionals compared to PBE. Globally, the new functionals exhibit much better balance in predicting thermodynamic and kinetic properties than any competing non-empirical GGA. (C) 2016 Elsevier B.V. All rights reserved.